Finely, divided, precipitated silica with high structure, method of its preparation and use

ABSTRACT

Finely divided precipitated silica for use as a delustering agent with high structure and a 
     
         ______________________________________                                    
 
    
     BET surface (DIN 66 132)                                                  
                   of 150 to 350 m 2  /g                               
Stamping density (DIN 53 194)                                             
                   between 60 and 120 g/l                                 
DBP absorption number                                                     
                   between 3.0 and 4.0 ml/g                               
Particle size distribution                                                
                   at least 70% from 1 to                                 
                   6 μm                                                
______________________________________                                    
 can be prepared by heating a mixture of water and sodium silicate under
 agitation to a temperature of 70° to 80° C., adding
 concentrated sulfuric acid into this mixture until half of the alkali
 present has been neutralized, shearing the reaction mixture and optionally
 raising the temperature at the same time to 86°±5° C.
 Concentrated sulfuric acid is added after a period of 30 to 120 minutes at
 a rather high rate until the pH of the silica suspension produced is 3.0
 to 3.5. The resulting silica suspension is ultimately filtered off by
 known filter devices, the silica filter cake washed free of sulfate, and a
 dry product is ultimately obtained.

REFERENCE TO A RELATED APPLICATION

The present application is a continuation of our copending application Ser. No. 07/483,968 filed Feb. 15, 1990, now abandoned, which in turn is a continuation of our copending application Ser. No. 07/347,654 filed May 5, 1989, now abandoned, the entire disclosures of which applications are relied on and incorporated herein by reference.

INTRODUCTION AND BACKGROUND

The present invention relates to a finely divided silica with high structure, a method of preparing the silica and the use of the silica as a delustering agent in films of the paint, lacquer, varnish and enamel type.

It is known that the delustering capacity of a silica depends on various factors such as e.g. the type of silica, the particle size, the refraction index and also on the vehicle system. Particle form and particle-size distribution of the secondary particles as well as the total effective specific particle volume are of particular significance.

A number of other requirements are placed on delustering silicas in addition to high efficiency, expressed by the reduction of the degree of glossiness in comparison to a non-matte paint film. Thus, for example, the drying behavior of the film coatings should not be adversely affected, no excessive thickening of the paint coating system should occur and the scratch resistance of the film coatings should not be lowered by the silica added. The behavior in suspension of the silica is an important point. The tendency of silica to settle and to form hard sediment which can only be stirred up again with difficulty can be prevented or at least improved by a number of measures. Thus, for example, DE-AS 15 92 865 describes the impregnation of silica during the preparation process by means of wax emulsions.

The addition of synthetic silica as delustering agent is known. See for example the publications:

    ______________________________________                                                  EPO-Patent 0,008,613                                                           German Patent 24 14 478                                                        German DAS 17 67 332                                                           German OLS 16 69 123                                                           German DAS 15 92 865.                                                 ______________________________________                                    

Numerous methods of preparing synthetic silica are also known (cf. Ferch in "Chem.-Ing.-Techn." 48, pp. 922-33 (1976)).

According to German Patent 24 14 478, aerogel-like delustering agents can be obtained by the structuring of pyrogenically prepared silica. To this end, pyrogenic silica is moistened with alkaline adjusted water, ground and dried. This procedure of preparing delustering agents is complicated and expensive.

The delustering agent according to German Patent 24 14 478 is an excellent delustering agent. However, it has the disadvantage that it thickens the film compositions too heavily. A solvent must therefore be added in addition for working with a spray gun to facilitate application of the films to a surface to be coated.

A wax-coated precipitated silica acid is prepared according to the process described in DE-PS 15 92 865 and is used as delustering agent. This delustering agent has the disadvantage, however, that the paints prepared with it exhibit an undesirable blue bloom on dark surfaces.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a finely divided precipitated silica of high structure with certain desired characteristics and especially to achieve a great savings of solvent while retaining the desired delustering action.

Another object of the invention is to prepare a waxcoated delustering agent which does not exhibit a blue bloom and has a better delustering action.

In more particular detail, an object of the present invention is to provide finely divided precipitated silica with a high structure and the following characteristics:

    ______________________________________                                         BET surface (DIN 66132)                                                                          between 150 and 350 m.sup.2 /g                               Stamping density (DIN 53194)                                                                     between 60 and 120 g/l                                       DBP number        between 3.0 and 4.0 ml/g                                     Particle size distribution                                                                       at least 70% from 1 to 6 μm                               (measured with a Coulter                                                       counter)                                                                       (The determination is                                                          performed according to                                                         DE-PS 17 67 332, column 2,                                                     lines 30-64.)                                                                  ______________________________________                                    

In order to determine the particle size with a Coulter counter, approximately 0.5 g silica acid are dispersed in 50 ml isotonic solution of common salt (0.5% NaCl and 0.089% Na₄ P₂ O₇. 10 M₂ O in distilled water) with a magnetic stirrer and subsequently treated for 1 minute with supersonics (200 watts). This suspension is added to 200 ml isotonic solution of common salt and agitated.

A measuring capillary tube is immersed into the agitated suspension and an electric field is applied thereto. When the particles pass through the measuring capillary tube, the electric field is varied as a function of the particle size.

It is still a further object of the invention to provide a method for preparing finely divided precipitated silica with a high structure processing the following characteristics:

    ______________________________________                                         BET surface (DIN 66 132)                                                                         of 150 to 350 m.sup.2 /g                                     Stamping density (DIN 53 194)                                                                    between 60 and 120 g/l                                       DBP number        between 3.0 and 4.0 ml/g                                     Particle size distribution                                                                       at least 70% from 1 to 6 μm.                              ______________________________________                                    

The method of the invention is characterized by forming a mixture of water and sodium silicate which is then heated under agitation to a temperature of 70° to 80° C. Concentrated sulfuric acid is then dosed into this mixture until half of the alkali (sodium) present has been neutralized. The reaction mixture is treated by a shearing unit and, optionally, the temperature raised at the same time to 86°±5° C. Concentrated sulfuric acid is added after a waiting period of 30 to 120 minutes at a rather high rate of addition until the pH of the silica suspension produced is 3.0 to 3.5. The silica suspension is optionally diluted with water and the coarse portion optionally separated by a centrifugal pump and a hydrocyclone. The silica is filtered off by known filter devices and the resulting silica filter cake is washed free of sulfate. Then, the silica filter cake is redispersed with the addition of water using an agitator unit to form a suspension with a solid content of 80±10 g/l. Alkyl dimethylbenzyl ammonium chloride is optionally added to this suspension, and the suspension obtained in this manner is spray-dried. The recovered dried product can then be ground, if desired.

DETAILED DESCRIPTION OF THE INVENTION

In carrying out the present invention, silica particles are prepared with particle diameters in a particle-size range of 1 to 6 μm. Particles smaller that 1 μm are ineffective for delustering purposes and generally cause an undesirable thickening of the film vehicle. On the other hand, particles which are too large result in a disadvantageous roughness of the surface in the film coating. The object is to control appropriate sizes during the precipitation reaction and to retain chosen particle sizes by suitable measures until the finished product is obtained. In order to assure that all particles find the same conditions of growth, the entire charge of water glass starting material is put into a receiver at the beginning of the process for production. The addition of sulfuric acid is performed in two steps. In the first step, the addition of acid is measured in such a manner that the silica begins to flocculate after the end of the first stage of the addition of the acid. During this growth phase, in order to prevent an excessive particle growth, shearing is performed in addition to the agitation. The addition of acid remains interrupted until the desired particle spectrum has been achieved. Subsequently, the remaining alkali content of the water glass is neutralized in a second stage, during which shearing is continued. After a slightly acidic pH has been achieved, the precipitation reaction is terminated.

The concentrated sulfuric acid used for purposes of the present invention is conventional and, for example, is in the range of D=1.75 to 1.85 and 90 to 97% by weight.

The silica suspension is worked up and conditioned in the customary manner. There is the possibility that hard and coarse particles are produced in the course of the reaction by local excess acidifying. These undesired particles can be removed from the suspension with the aid of a hydrocyclone. The filtration of the suspension is performed e.g. with a plate-and-frame press in which the filter cake is washed free of sulfate. The washed filter cake is redispersed in water, a cationic tenside is optionally added and the product is then spray-dried. The cationic tenside (surfactant) brings about a displacement of the water from the particle surface thereby even in the aqueous phase, which suppresses to a great extent the shrinking process which takes place during the drying process. In this manner, it is possible to prevent the particles from clumping together to rather large, solid formations during drying. Depending on the desired degree of fineness, the silica can be used as is or additionally ground. As a result of the procedure described herein, a light grinding is sufficient, that is, only little grinding energy need be expended in order to disagglomerate the particles again.

The precipitated silica of the present invention can be used as delustering agent in a wide variety of film coatings such as paints, varnishes, lacquers and the like.

It has the advantage that no additional solvent need be used.

In order to improve the sedimenting behavior of the silica products in coating film compositions, an impregnation with emulsions is carried out in accordance with the disclosure of DE-PS 15 92 865, incorporated herein by reference.

A still further object of the invention is to provide a precipitated silica which is coated by an emulsion and prepared from the precipitated silica in accordance with the present invention. In this aspect of the invention, the coating can take place according to the known method of DE-PS 15 92 865 which corresponds to U.K. Patent 1,236,775, the entire disclosure of which is relied on and incorporated by reference.

The coated precipitated silica exhibits a carbon content of 1 to 8% by weight in addition to the same physical and chemical characteristic data of the uncoated precipitated silica.

In one embodiment of the invention, the precipitated silica can be coated by a silicon oil emulsion.

This precipitated silica can be used as delustering agent in paints, varnishes, lacquers and the like.

In a further particular embodiment of the invention, the precipitated silica can be coated by a polyethylene wax emulsion.

This precipitated silica product can be used as delustering agent in paints, varnishes, lacquers and the like.

It is especially advantageous that the precipitated silica coated with the wax emulsion does not generate a blue bloom in the paint surfaces.

All manner of film forming components can be combined with the delustering agents of the invention.

The following examples serve to illustrate the details of the present invention.

The method of the invention is carried out in known apparatuses.

The core of the precipitation apparatus used herein is a hard-rubberized, double-jacketed vessel with a volume of 120 liters which is provided with an agitator mechanism. Potential agitators suitable for the invention are e.g. anchor mixers, straight-arm paddle agitators or turbines. The reaction vessel can be heated with oil as heat carrier and thermostatted via the double jacket. A discharge pipe or tube is fixed to the bottom of the reaction vessel which pipe comprises a branch line in front of the bottom discharge valve. This branch runs to a shearing unit (Dispax reactor) with which the content of the reaction vessel can be rotated. The rotated precipitation suspension can be reintroduced into the top of the reaction vessel via the pipeline fixed to the pressure side of the shearing unit. The addition of water glass takes place either via a dosing pump from a storage vessel or directly from a vat by a vat pump. The sulfuric acid is dosed from a storage vessel by a dosing pump.

The precipitation suspension is pumped for filtration with the aid of a positive-displacement pump into a plate-and-frame press on which the filter cake produced is washed free of sulfate with water.

The washed filter cake is either placed on metal sheets and dried in a drying oven or is dispersed in water and spray-dried.

The dried silica can be subsequently ground. The product dried in a drying oven must generally be pre-ground in a toothed-disk mill before the fine grinding by means of a pin mill or air-jet mill. The spray-dried product can either be used directly or subjected to a fine grinding.

The efficiency of the non-coated precipitation silica prepared according to Examples 1-6 is compared in a black baking varnish with the product prepared according to DE-PS 24 14 478. In addition to the solvent requirement, the degree of glossiness according to Lange at a reflection angle of 60° and the grindometer value according to Hegman are evaluated.

For the determination of the degree of glossiness, which is a measure for the delustering power of the tested delustering silica, the gloss meter according to B. Lange, which is often used in Germany, is used. The Lange gloss meter uses an angle of 45° as incident and reflection angle. The measured degrees of glossiness are indicated in percents. The smaller their value, the better the delustering capacity of the silica tested, or, in other words, the less delustering agent needs to be used in order to achieve a quite specific degree of gloss.

The determination of grindometer value is carried out with the aid of a grindometer. The grindometer value, which is measured in μ, is a measure for the coarsest particles located in the finished, sprayable film composition mixture after the delustered silica has been stirred in. It can be related to the formation of specks in the dry paint film. The feared and undesired "spray grain" can be recognized with the aid of the grindometer.

The paint used has the following composition:

7.5 parts by weight paint prepaste Tack® 1

47 parts by weight fatty-acid modified alkyd resin 60% in xylene (Alftalat AR 481 m)

24 parts by weight melamine resin Maprenal MF 800 55% in isobutanol

6 parts by weight butanol

10.5 parts by weight xylene

1 part by weight silicon oil Baysilon paint additive OL 17 1% in xylene.

2.6 parts by weight product are worked in at a time. The working in is carried out by ten-minute agitation with a wing agitator at 2000 rpms. The paint is sprayed onto metal sheets in a dry layer approximately 30 μm thick, air-dried and annealed 30 min. at 180° C.

The values determined can be gained from table 2 below.

Example 1

66 kg Water and 21 kg soda water glass (d=1.35 g/cm³ ; ratio SiO₂ :Na₂ O=3.3) are added into the precipitation vessel and the mixture heated under agitation to 75° C. Concentrated sulfuric acid (d=1.83) is dosed into the precipitation mixture at a rate of 1.45 l/h. After 25 minutes of precipitation time, the shearing unit (Dispax reactor) is switched on. Shortly after the end of the addition of acid, silica begins to flocculate and the temperature of the precipitation is raised to 85° C. The supply of acid is interrupted for 20 minutes (waiting stage). After 50 minutes, the further addition of acid takes place with 1.8 l/h over a period of 15 minutes. The silica suspension produced exhibits a pH of 3.4 thereafter. The shearing unit is then cut off.

The suspension is diluted with 28 l water and conveyed by means of a centrifugal pump with 4.5 bars supply pressure onto a hydrocyclone. The ratio of coarse material suspension to fine material suspension is 1:12.

The fine material suspension is passed over a plate-and-frame press and washed sulfate-free.

The washed filter cake is redispersed using an Ultra-Turrax with the addition of water in such a manner that a suspension of 80 g/l is produced. An alkyl dimethylbenzyl ammonium chloride (BARQUAT®) is added to the suspension, so that 0.8 g/l active substance is present in the suspension.

This suspension runs through a sieve with a mesh size of 120 μm, which retains coarse foreign particles. The suspension is spray-dried immediately thereafter. The atomization takes place by means of a two-fluid nozzle.

The dried product has the following physical and chemical properties:

    ______________________________________                                         pH (DIN 53200)         6.0                                                     Water content (DIN)    4.8%                                                    Specific surface (DIN 66132)                                                                          272 m.sup.2 /g                                          DBP absorption (ml/g)  3.7                                                     Stamping density (DIN 53194)                                                                          87 g/l                                                  Particle size distribution                                                     (Coulter counter)                                                              <1 μm                5%                                                     1-6 μm              84%                                                     >6 μm               11%                                                     ______________________________________                                    

EXAMPLES 2-5

Precipitated silica is prepared as described in Example 1 with the sole difference that the time of the interruption of the addition of acid (equal to the waiting stage) is varied.

The physical and chemical data of the silica products obtained are ser forth in Table 1 below.

EXAMPLE 6

A precipitated silica is prepared as described in Example 1. In contrast to Example 1, the heating to 85° C. during the second phase of the addition of acid is eliminated. The waiting stage is 30 minutes.

The physical and chemical data of the precipitated silica obtained in this was set forth in Table 1 below.

EXAMPLE 7

A precipitated silica is prepared as described in Example 1. In contrast to Example 1, the waiting stage is 60 minutes. After the end of precipitation, 3.4 kg of an emulsion of silicon oil are added into the precipitated silica suspension.

The emulsion is prepared as follows:

0.24 parts by weight Emulan AF are dissolved in 80 parts by weight water. 20 parts by weight Baysilon oil® AC 3031 are added under dispersion with an Ultra-Turrax.

The work-up of the precipitated silica suspension takes place as described in Example 1. The spray-dried precipitated silica is subsequently ground in an air-jet mill.

The physical and chemical data for this product are set forth in Table 3 below.

EXAMPLE 8 (Coating With Polyethylene Wax Emulsion)

A precipitated silica is prepared as described in Example 1. The waiting stage is 90 minutes. 45 l of the fine material suspension obtained is compounded with 625 g of a wax emulsion under agitation. The wax emulsion is prepared in an autoclave which can be heated with vapor and is provided with a dispenser. 4.8 parts by weight of an alkyl polyglycol ether (Marlowet® GFW) are first dissolved in 81.0 parts by weight water at approximately 100° C. Then, 14.2 parts by weight low-pressure polyethylene wax are added and heated to 130° C. When 130° C. has been reached, the dispenser is turned on and the mixture dispersed for 30 minutes. During this time, the temperature is maintained between 130° C. and 140° C. After the dispenser has been turned off and the mixture cooled off to approximately 110° C., the finished emulsion is discharged.

The polyethylene wax used is characterized by the following characteristics:

    ______________________________________                                         Average molecular weight                                                                              1000                                                    Solidification point   100-104° C.                                      Drop point             110-117° C.                                      Density (g/cm.sup.3)   0.93.                                                   ______________________________________                                    

The precipitated silica suspension is worked up as described in Example 1. The spray-dried precipitated silica is then ground in an air-jet mill.

The physical and chemical data for this product are set forth in Table 3 below.

EXAMPLE 9 (Coating With Polyethylene Wax Emulsion)

A precipitated silica is prepared as described in Example 1. The waiting stage is 90 minutes. 45 l of the fine material suspension obtained is compounded with 860 g of a wax emulsion under agitation. The wax emulsion is prepared in an autoclave which can be heated with vapor and is provided with a dispenser apparatus. 4.8 parts by weight of an alkyl polyglycol ether (Marlowet® GFW) are first dissolved in 81.0 parts by weight water at approximately 100° C. Then, 14.2 parts by weight low-pressure polyethylene wax are added and heated to 130° C. When 130° C. has been reached, the dispenser is turned on and the mixture dispersed for 30 minutes. During this time, the temperature is maintained between 130° C. and 140° C. After the dispenser apparatus has been turned off and the mixture cooled off to approximately 110° C., the finished emulsion is discharged.

The polyethylene wax used has the following characteristics:

    ______________________________________                                         Average molecular weight                                                                              2700                                                    Solidification point    92-96° C.                                       Drop point             102-110° C.                                      Density (g/cm.sup.3)   0.92.                                                   ______________________________________                                    

The precipitated silica suspension is worked up as described in Example 1. The spray-dried precipitated silica is then ground in an air-jet mill.

The physical and chemical data are set forth in Table 3 below.

EXAMPLE 10

The technical applications capabilities of the precipitated silicas obtained according to examples 7,8 and 9 are compared in three test-paint formulations with a delustering agent prepared according to DE-PS 15 92 865. The data is compiled in Table 4 below.

The determination of the degree of glossiness is performed with gloss-measuring devices according to Lange and Gardner (ASTM D 523-53 T). According to Lange, the incidence and reflection angles are 45°, according to Gardner 60° and 85°. The grindometer value is determined according to ISO 1524 in black stoving lacquer.

The text-paint formulations and the method of procedure are described below.

A) Black stoving lacquer

    ______________________________________                                                              parts by wt.                                              ______________________________________                                         Paint prepaste TACK ® 1                                                                           7.5                                                     Alkydal ® R 40/60% in xylene                                                                      47.0                                                    Maprenal ® MF 800/55% in isobutanol                                                               24.0                                                    Butanol                5.0                                                     Ethyl glycol           3.0                                                     Xylene                 8.5                                                     Butyl glycol           3.0                                                     Baysilon ® oil OL 17 1% in xylene                                                                 2.0.                                                    ______________________________________                                    

5 g precipitated silica as the delustering agent are stirred into 100 g paint with a wing agitator at 2000 rpms for 8 minutes. The viscosity of the mixture is set with xylene to a discharge time of 20 seconds (Ford beaker, DIN 4 mm nozzle).

The paint is sprayed onto metal sheets in a dry layer approximately 30 m thick, air-dried and annealed 30 min. at 180° C.

B) Polyester paint (UP paint)

    ______________________________________                                                               parts by wt.                                             ______________________________________                                         Roskydal ® 500 A    36.0                                                   Roskydal ® tix 18   4.0                                                    Tert. butyl catechol 1% in monostyrene                                                                 0.5                                                    Aerosil ® 200       0.3                                                    Barite, ground          20.0                                                   Bayer titanium R-FD-1   10.5                                                   Green pigment 600       1.5                                                    Baysilon ® oil OL 17 1% in toluene                                                                 2.0                                                    Ethyl acetate           6.0                                                    Monostyrene             18.4                                                   Octa-Soligen cobalt in toluene (2.2% Co)                                                               0.8.                                                   ______________________________________                                    

6.5 g precipitated silica as the delustering agent are added to 100 g of this paint mixture before processing and dispersed 8 minutes at 2000 rpms with a wing agitator. The viscosity of the mixture is adjusted with ethyl acetate to a run-off time of 20 seconds (Ford beaker, DIN 4 mm-nozzle). The paint mixture is applied in layer thicknesses of approximately 80 μm.

C) DD paint

    ______________________________________                                                            parts by wt.                                                ______________________________________                                         Desmophen ® 800  10.0                                                      Desmophen ® 1700 20.0                                                      NC-Chips E 730       4.0                                                       Butyl acetate 98%    18.0                                                      Ethyl glycol acetate 22.8                                                      Butoxyl              5.0                                                       Shellsol ® A     20.0                                                      Baysilon oil OL 17 10% in xylene                                                                    0.2.                                                      ______________________________________                                    

10.8 g delustering agent and 36 g Desmodur® L/75% in ethyl acetate are added to 100 g of the above mixture and dispersed 8 minutes at 2000 rpms with a wing agitator. The mixture is adjusted with ethyl acetate to a run-out time of 18 seconds (DIN beaker, 4 mm nozzle according to DIN 53211). The application is performed in layer thicknesses of 30-40 μm.

Table 4 shows that a distinct improvement of the delustering action can be determined in all test paint formulations over the state of the art.

                                      TABLE 1                                      __________________________________________________________________________     Waiting          Water Specific    Stamping                                    Stage            Content                                                                              surface                                                                              DBP   density                                                                              Grain-size distribution               Time       pH    DIN 55921                                                                            DIN 66132                                                                            absorption                                                                           DIN 53194                                                                            (Coulter counter)                     (min.)     DIN 53200                                                                            (%)   (m.sup.2 /g)                                                                         (ml/g)                                                                               (g/l) <1 μm                                                                           1-6 μm                                                                          >6 μm                      __________________________________________________________________________     Example 1                                                                            20   6.0   4.8   272   3.7   87     5  84  11                            Example 2                                                                            30   6.0   5.3   300   3.8   80     7  85  8                             Example 3                                                                            45   5.2   5.7   239   3.7   82    10  85  5                             Example 4                                                                            60   5.8   6.4   244   3.4   86    15  84  1                             Example 5                                                                            90   5.9   3.9   278   3.8   76    15  83  2                             Example 6                                                                            30   6.4   7.7   316   3.8   103    3  84  13                            __________________________________________________________________________

                                      TABLE 2                                      __________________________________________________________________________                     Parts by wt.                                                             Viscosity                                                                            Solvent per                                                              DIN 4 mm                                                                             processing                                                                            Grindometer                                                                           5 = % gloss 60°                           Product   sec.  consistency                                                                           value in μm                                                                        length                                           __________________________________________________________________________     From Example 1                                                                           33    1.5    50     38.5                                             From Example 2                                                                           33    1.5    37     40.5                                             From Example 3                                                                           32    --     28     42.5                                             From Example 4                                                                           38    4.5    30     38.5                                             From Example 5                                                                           31    --     28     47.0                                             From Example 6                                                                           33    --     47     38.0                                             Reference product                                                                        39    5.5    40     38.5                                             according to DE-PS                                                             24 14 478                                                                      __________________________________________________________________________

                                      TABLE 3                                      __________________________________________________________________________                    Water Specific    Stamping                                                     Content                                                                              surface                                                                              DBP   density                                                pH    DIN 55921                                                                            DIN 66132                                                                            absorption                                                                           DIN 53194                                                                            Carbon                                           DIN 53200                                                                            (%)   (m.sup.2 /g)                                                                         (ml/g)                                                                               (/gl/)                                                                               content (%)                             __________________________________________________________________________     From Example 7                                                                          6.2   4.7   250   3.7   64    1.7                                     From Example 8                                                                          6.7   4.9   213   3.5   83    3.5                                     From Example 9                                                                          6.7   4.9   203   3.6   79    4.0                                     __________________________________________________________________________

                                      TABLE 4                                      __________________________________________________________________________               Black Stoving Varnish                                                                      UP paint       DD paint                                            Grindometer                                                                           Gloss 45°                                                                    Gloss 45°                                                                    Gloss 40°                                                                    Gloss 85°                                                                    Gloss 45°                                                                    Gloss 60°                                                                    Gloss 85°                Product   value in μm                                                                        Lange                                                                               Lange                                                                               Gardner                                                                             Gardner                                                                             Lange                                                                               Gardner                                                                             Gardner                         __________________________________________________________________________     From Example 7                                                                           28     2.5  17   26   49   5.5   9   18                              From Example 8a                                                                          30     2.5  8    13   22   6.5  10   17                              From Example 8b                                                                          30     2.5  13.5 21   40   4.5   9   13                              Delustering                                                                              26     4.5  44.5 59   86   22.5 36   68                              agent according                                                                to DE-PS 15 92 865                                                             __________________________________________________________________________

The trade designations used in the examples have the following meanings:

    ______________________________________                                         Paint prepaste Tack ® 1                                                    Product      Composition (% by wt.)                                            ______________________________________                                         Carbon black paste 1                                                                        18 pigment carbon black of class HCC                                           36 alkyd resin based on soya bean                                              46 solvent                                                        Alftalat AR 481 m                                                              Characteristic:                                                                             Short or medium oily, drying alkyd resins.                        Areas of application:                                                                       Stoving varnishes and stoving first coats                                      for metallic surfaces. Acid-hardening                                          paints. Nitrocellulose combination paints.                        ______________________________________                                                                 Alftalat                                                                       AR 481 m                                               ______________________________________                                         Composition of the                                                             100% resin (approximate)                                                       Oil content (triglyceride)    48%                                              Phthalic acid anhydride       39%                                              Viscosity                                                                      Run-out time 4, DIN 53211/29° C. s                                                                    50-70                                            23° C. s               40-60                                            Dynamic viscosity                                                              DIN 53177/20° C.                                                                           mPa · s                                                                          215-300                                          23° C.      mPa · s                                                                          175-250                                          Color value                                                                    Iodine color value DIN 6162                                                                       mg I/100 cm.sup.3                                                                         <15                                              Gardner color standard         <7                                              ASTM D 1544                                                                    Acid value         mg KOH/g   25                                               DIN 53402                                                                      Density (delivered form)                                                                          g/cm.sup.3 approx. 1.02                                     20° C.                                                                  Content of non-volatile                                                                           %          approx. 60                                       portions                                                                       DIN 53216 (2 g + 2 cm.sup.3                                                    toluene/1 h 125° C.)                                                    Flash point (delivered form)                                                                      °C. approx. 27                                       DIN 53213                                                                      ______________________________________                                    

Maprenal MF 800

Characteristic: Non-plasticizied, isobutyl-etherified melamine formaldehyde resins.

    ______________________________________                                                                 Maprenal                                                                       MF 8 800                                               ______________________________________                                         Viscosity (delivered form)                                                     Run-out time 4, DIN 53211/20° C. s                                                                    60-90                                            23° C. s               50-80                                            Dynamic viscosity                                                              DIN 53177/20° C.                                                                           mPa · s                                                                          250-430                                          23° C.      mPa · s                                                                          220-360                                          Color value (delivered form)                                                   Iodine color value DIN 6162                                                                       mg I/100 cm.sup.3                                                                         <1                                               Gardner color standard        <1                                               ASTM D 1544                                                                    Acid value         mg KOH/g   <1                                               DIN 53402                                                                      Density            g/cm.sup.3 approx 0.99                                      20° C.                                                                  Gasoline compatibility                                                                            cm.sup.3 /1 g                                                                              5-10                                            (n-heptane)DIN 53 187                                                          melamine resin                                                                 (delivered form)                                                               Content of non-volatile                                                                           %          approx. 55                                       components (delivered form)                                                    DIN 53216 (2 g + 2 cm.sup.3)                                                   Butanol/1 h 120° C.)                                                    Flash point (delivered form)                                                                      ° C.                                                                               approx. 31                                       DIN 53 213                                                                     ______________________________________                                    

Baysilone paint additive OL 17

Polyether-modified methyl polysiloxane

    ______________________________________                                         Delivery tolerances:                                                                       appearance     clear, yellowish                                                iodine color   max. 3                                                          value, DIN 6162                                                                viscosity, DIN 53015                                                                          650-850 mPa · s                                        23° C.                                                      Other characteristic                                                                       density, DIN 53217                                                                            1.025-1.050 g/ml                                    data:       20° C.                                                                  flash point,   approx. 80 C.                                                   DIN 51758                                                                      surface tension,                                                               DIN 53914, 23° C.                                                                      approx. 21 mN/m                                                 with Harkins-Jordan                                                            correction                                                                     refractive index,                                                                             1.447-1.451                                                     23° C.                                                      Solubility: gasoline hydrocarbons                                                                         u/l                                                             benzene hydrocarbons                                                                           l                                                              alcohols        l                                                              esters          l                                                              ketones         l                                                              glycol ethers   l                                                              glycol ether acetates                                                                          l                                                              explanations:  l = soluble                                                                    u = insoluble                                       ______________________________________                                    

Baysilon oil® AC 3031

Chemical characterization polysiloxane diol

    ______________________________________                                         Physical data                                                                  ______________________________________                                         Melting temperature                                                                              <-60° C. (setting point)                              Softening temperature                                                          Boiling temperature                                                                              above approx. 130° C.                                 Decomposition temperature                                                                        °C.                                                   pH                approx. 7-8 (at 20 g/l water)                                Solubility in water                                                                              insoluble at 20° C.                                   Intrinsic odor    distinct intrinsic odor                                      State (20° C.)                                                                            liquid                                                       Vapor pressure (20° C.)                                                                   <100 mbars                                                   Density (20° C.)                                                                          0.98 g/ml                                                    ______________________________________                                    

    ______________________________________                                         Emulan AF                                                                      ______________________________________                                         Chemical         medium-highly ethoxylated fatty                               character        alcohol, non-ionic                                            Solubility       Dissolves well and usually also                               (at 25° C., 10%)                                                                         clear in mineral oils, fatty oils,                                             molten paraffins and fats.                                                     Dissolves clear in most organic                                                solvents.                                                     Chemical character                                                                              fatty alcohol ethoxylate                                      Consistency      like soft wax                                                 (room temperature)                                                             Acid value (DIN 53402)                                                                          pract. 0                                                      Saponification value                                                                            pract. 0                                                      (DIN 53 401)                                                                   pH (1% aqueous solution                                                                         6-7.5                                                         or dispersion)                                                                 Active substance pract. 100%                                                   content                                                                        Density (c/cm.sup.3)                                                                            approx. 0.91                                                  (20° C.)(DIN 53757)                                                                      (50° .C)                                               Viscosity (mPa · s)                                                                    --                                                            (20° C.) (DIN 53015)                                                    Melting point    approx. 42° C.                                         Solidification point                                                                            --                                                            Drop point (DGF M-III-3)                                                                        --                                                            Flash point (DIN 51758)                                                                         approx. 190° C.                                        HLB value (W. C. Griffin)                                                                       approx. 11                                                    Chief active tendency                                                                           oil in water                                                  (Emulsion type)                                                                Solubility tendency                                                                             in mineral oil and polar                                                       organic media                                                 ______________________________________                                         Alkydal R 40                                                                   ______________________________________                                         Short-oily alkyd resin based on ricin oil                                      Oil content/triglyceride                                                                        approx. 40%                                                   Phthalic acid anhydride                                                                         approx. 38%                                                   Density/20° C.                                                                           approx. 1.13 g/cm.sup.3                                       OH content       2.5%                                                          Delivery tolerance                                                             Iodine color number/50%                                                                         max. 5                                                        solution                                                                       Acid value/solvent-free                                                                         20-30                                                         Viscosity/20° C. delivery form                                                           3500-4500 mPa · s (cP)                               Flash point      approx. 27° C.                                         ______________________________________                                         Roskydal 500 A                                                                 ______________________________________                                         Unsaturated polyester resin (glossy polyester), reactive,                      hardens hard                                                                   Delivery tolerance.sup.1                                                       Non-volatile portion                                                                            74-77%                                                        Hazen color      max. 100                                                      Acid value/delivery form                                                                        10-20                                                         Viscosity/20° C.                                                                         2200 . . . 2600 mPa · s                              Other data:                                                                    Density/20° C.                                                                           approx. 1.12 g/cm.sup.3                                       Flash point      approx. 37° C.                                         ______________________________________                                          .sup.1 test methods according to DIN 58184                               

Roskydal tix 18

Thixotropic, unsaturated polyester resin (paraffin type), reactive

    ______________________________________                                          Supply tolerance.sup.2                                                        ______________________________________                                         Non-volatile portion 49 . . . 53%                                              Iodine color value   max. 2                                                    Acid value/delivery form                                                                            max. 15                                                   Viscosity 20° C.                                                                             thixotropic flow                                                               behavior                                                  Flash point          approx. 32° C.                                     ______________________________________                                          .sup.2 test methods according to DIN 53184                               

    __________________________________________________________________________     Bayertitan R-FD-1                                                                                       Brightening                                                                              Rel.                                                          Oil Number                                                                            Capacity according                                                                       Scattering                                                                            Density                                                [adsorption]                                                                          to Reynolds                                                                              Power  according                                       Additional                                                                            according to                                                                          according to                                                                             according to                                                                          to                                   Bayertitan                                                                           % TiO.sub.2                                                                         Components                                                                            DIN 53 199                                                                            DIN 53 192                                                                               DIN 53 165                                                                            DIN 53 193                           __________________________________________________________________________     F-FD-1                                                                               96   Al.sub.2 O.sub.3                                                                      19     1900 750  112    4 ·                         __________________________________________________________________________

    ______________________________________                                         Green pigment 6001  Green pigment 6001                                         ______________________________________                                         Color index No.     77 335                                                     Color index pigment 19                                                         Chemical composition                                                                               Co--Al--Ti--Ni                                                                 Zn oxide                                                   Oil number (1) g/100 g                                                                             20                                                         Drying loss (2) %   max. 0.5                                                   Stamping density (3) g/l                                                                           1600                                                       Sieve residue (4) % max. 0.1                                                   Color strength (7)  --                                                         Covering capacity   190                                                        value (8) %                                                                    Particle size (TEM) m                                                                              0.15-2.0                                                   Density (9) g/cm.sup.3                                                                             5.0                                                        Water-soluble       max. 0.5                                                   portion (10) %                                                                 Spec. surface (11) m.sup.2 /g                                                                      --                                                         pH (12)             8.5-9.5                                                    Heat resistance °C.                                                                         >500                                                       Light resistance/   8                                                          full shade (13)                                                                TiO.sub.2 mixture 1:1                                                                              8                                                          TiO.sub.2 mixture 1:10                                                                             8                                                          Weather resistance/ very good                                                  full shade                                                                     Acid resistance     very good                                                  Alkali resistance   good                                                       Lime resistance     good                                                       Solvent resistance  very good                                                  Migration resistance                                                                               very good                                                  ______________________________________                                          Explanation of the footnotes:                                                  (1) according to DIN ISO 787/V, ASTM D 281 or JIS K 5101/9                     (2) according to DIN ISO 787/II, ASTM D 280 or JIS K 5101/21. In the case      of VOSSEN blue, the reweighing is performed immediately after removal of       the specimen from the drying oven in a hot state.                              (3) according to DIN ISO 787/XI of JIS K 5101/18                               (4) Cd, Co and Ti pigments according to DIN 53 195 (0.045 μm sieve)         VOSSEN blue according to DIN ISO 787/XVIII, (0.040 sieve) [sic], ASTM D        1714 or JIS K 5101 20                                                          (5) according to ISO 787/I                                                     (6) according to ISO 787/XVI                                                   (7) according to DIN 53 204 and DIN 53234                                      (8) soft in PVC, TiO2 RN 56 = 100%                                             (9) according to DIN ISO 787/X or JIS K 5101/17                                (10) according to DIN ISO 787/III or JIS K 51010/22                            (11) according to DIN 66 131                                                   (12) according to DIN ISO 787/IX, ASTM D 1208 or JIS K 5101/24                 (13) according to DIN 54 003 or JIS K 5101/15                            

Octa-Solingen cobalt

Octa-Solingen cobalt is a dry substance which contains 16% Co in addition to 2-n ethyl hexanoic acid (C₈ H₁₆ O₂).

    ______________________________________                                         Desmophen 800                                                                  ______________________________________                                         Heavily branched polyester containing hydroxyl groups.                         Characteristic values                                                          Delivery form  100%        approx. 85%                                         Hydroxyl content:                                                                             approx. 8.8%                                                                               approx. 7.5%                                        Acid value:    <4          <4                                                  Color value according                                                                         7-10*       3-8*                                                to DIN 6162:                                                                   Flash point according                                                          to DIN 51 758: >200° C.                                                                            --                                                  to DIN-EN 53   --          approx. 49° C.                               Density at 20° C.                                                                      1.14 g/cm.sup.3                                                                            approx. 1.11 g/cm.sup.3                             according to DIN 51 757:                                                       Viscosity      900 ± 100                                                                               900 ± 100                                        (velocity gradient                                                                            mPas**      mPas**                                              D 150 s.sup.-1) at 20° C.:                                                             725 ± 75 725 ± 75                                         Water content: <0.15%      <0.15%                                              ______________________________________                                           *50% in ethyl glycol acetate                                                  **70% in ethyl glycol acetate                                            

Aerosil® 200

Aerosil® 200 is a pyrogenically prepared silicic acid with the following physical and chemical characteristic values:

    ______________________________________                                         Surface according to BET                                                                        m.sup.2 /g  200 ± 25                                       Average size of the primary                                                                     nanometer 12                                                  particles                                                                      Stamping density (1)                                                                            g/l         approx. 50                                        Drying loss (2) (2 h at 105° C.)                                                         %           <1.5                                              upon leaving the works                                                         Annealing loss (2)(6)                                                                           %           <1                                                (2 h at 1000° C.)                                                       pH (3) (in 4% aqueous        3.6-4.3                                           dispersion)                                                                    SiO.sub.2 (5)    %           >99.8                                             Al.sub.2 O.sub.3 (5)                                                                            %           >0.05                                             Fe.sub.2 O.sub.3 (5)                                                                            %           >0.003                                            TiO.sub.2 (5)    %           >0.03                                             HCl (5)          %           >0.025                                            Sieve residue (4) according                                                                     %           >0.05                                             to Mocker (45 m)                                                               ______________________________________                                    

Technical Data of the Aerosil Standard Types

1) according to DIN 53 194

2) according to DIN 55 921

3) according to DIN 53 200

4) according to DIN 53 580

5) in relation to the substance annealed 2 hours at 1000° C.

6) in relation to the substance dried 2 hours at 105° C.

7) HCl content is a component of the annealing loss

    ______________________________________                                         Desmophen 1700                                                                 ______________________________________                                         Linear polyester containing hydroxyl groups                                    Characteristic data                                                            Hydroxyl content:     approx. 1.2%                                             Equivalent weight:    approx. 1418                                             Color value according to DIN 6162*:                                                                  max. 5                                                   Flash point according to DIN 51758:                                                                  >200° C.                                          Density at 20° C. according to DIN 53217:                                                     approx. 1.19 g/cm.sup.3                                  Viscosity at 23° C.**                                                                         575 ± 75 mPa · s                             (velocity gradient D ≈ 190 s.sup.-1)                                   Water content:        >0.15%                                                   ______________________________________                                           *50% in ethyl glycol acetate                                                  **70% in ethyl glycol acetate                                            

NC-Chips E 730

NC-Chips E 730 is a collodion cotton [c.c. (wool), pyrocellulose, soluble nitrocellulose, pyroxyline]

Shellsol® A

Shellsol® A is a carbon solvent rich in aromatic hydrocarbons with the following data:

    ______________________________________                                         Boiling limits °C. ASTM D 107/86                                                                    160-182                                            Density at 12° C. ASTM D-1298                                                                       0.874                                              Flash point °C. AP IP 170 PM ASTM D-93                                                              47                                                 Evaporation number (ether = 1) DIN 53 170                                                                  46                                                  ##STR1##                    1.499                                             Color (Saybolt) ASTM D-156  +30                                                Viscosity 25° C. mm.sup.2 /s ASTM D-445                                                             0.810                                              Aniline [cloud] point ° C. = mixes ASTM D 611                                                       15                                                 Kauri-butanol value ASTM D-1133                                                                            90                                                 Aromatic hydrocarbon content vol. % ASTM D-1319                                                            19                                                 Surface tension at 20° C. mN/m ASTM D-971                                                           29.5                                               ______________________________________                                    

Desmodur L

Aromatic polyisocyanate

    ______________________________________                                                        75% delivery                                                                               67% delivery                                        Characteristic data                                                                           form        form                                                ______________________________________                                         NCO content*:  approx. 13% approx. 11.6%                                       Equivalent weight:                                                                            approx. 323 approx. 362                                         Color value according                                                                         max. 5      max. 5                                              to DIN 6162*:                                                                  Flash point according                                                                         approx. +1° C.                                                                      approx. -38° C.                              to DIN 53 213:                                                                 Density at 20° C.                                                                      approx. 1.17                                                                               approx. 1.15 g/cm.sup.3                             according to DIN 53217:                                                                       g/cm.sup.3                                                      Viscosity at 23° C.                                                                    1500 ± 400                                                                              1500 ± 400                                       (mPa · s)*                                                            Monomeric diisocyanate                                                                        >0.5%       >0.5%                                               content                                                                        ______________________________________                                          *Delivery specification                                                  

The term "DIN" stands for German industrial standard.

As will be apparent from the above, many different film forming components such as synthetic resins and mixtures with or without pigments are suitable for combination with the finely divided precipitated silica delustering agent of this invention. Further modifications and variations will be apparent to those skilled in the art and are intended to be encompassed by the claims appended hereto.

German priority application P 38 15 670.9-41 is incorporated and relied on herein. 

We claim:
 1. A finely divided precipitated silica with high structure having the following properties:

    ______________________________________                                         BET surface (DIN 66 132)                                                                          of 150 to 350 m.sup.2 /g                                    Stamping density (DIN 53 194)                                                                     between 60 and 120 g/l                                      DBP absorption number                                                                             between 3.0 and 4.0 ml/g                                    Particle size distribution                                                                        at least 70% from 1 to                                                         6 μm.                                                    ______________________________________                                    


2. A method of preparing finely divided precipitated silica with a high structure having the following properties:

    ______________________________________                                         BET surface (DIN 66 132)                                                                           of 150 to 350 m.sup.2 /g                                   Stamping density (DIN 53 194)                                                                      betweeen 60 and 120 g/l                                    DBP absorption number                                                                              between 3.0 and 4.0 ml/g                                   Particle size distribution                                                                         at least 70% from 1 to                                                         6 μm,                                                   ______________________________________                                    

comprising: forming a mixture of water and sodium silicate, heating said mixture under agitation to a temperature of 70° to 80° C., adding concentrated sulfuric acid to said mixture until half of the sodium present in the mixture has been neutralized, agitating the reaction mixture formed thereby by a shearing action after a waiting period of 30 to 120 minutes, adding sulfuric acid until the pH of the silica suspension produced thereby is 3.0 to 3.5, filtering the suspension to filter the silica off to obtain a silica filter cake, washing the silica filter cake to remove sulfate, dispersing the silica filter cake in water by the addition of water using agitation to form a suspension with a solids content of 80±10 g/l, and recovering the product.
 3. The method according to claim 2 wherein while shearing the reaction mixture is treated by heating to a temperature of 86°±5° C.
 4. The method according to claim 2 wherein the silica suspension is diluted with water after reaching the pH of 3.0 to 3.5.
 5. The method according to claim 2 wherein the suspension contains a portion which is separated by a centrifugal pump and a hydrocyclone.
 6. The method according to claim 2 wherein alkyl dimethylbenzyl ammonium chloride is added to the suspension after the silica filter cake is dispersed in water.
 7. The method according to claim 2 wherein the suspension is spray-dried to recover the product.
 8. The method according to claim 2 wherein the recovered product is dried and ground. 